JP2003088730A - Treatment method for reverse osmosis membrane element and reverse osmosis membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for a reverse osmosis membrane capable of keeping effect for reducing the concentration of a solute in water permeated through the reverse osmosis membrane for a long time and capable of separating even non-electrolyte organic matter or boron or the like not dissociated in a neutral region in a high blocking ratio, and a reverse osmosis membrane module. SOLUTION: In a membrane separator loaded with the reverse osmosis membrane element having a polyamide skin layer, the pressure container in the membrane separator is filled with the reverse osmosis membrane element and a free chlorine aqueous solution containing bromine is subsequently brought into contact with the reverse osmosis membrane element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation device equipped with a reverse osmosis membrane, in which the solute concentration in the reverse osmosis membrane permeate water obtained during operation is obtained by subjecting the installed reverse osmosis membrane element to a chemical treatment. The present invention relates to a method for treating a reverse osmosis membrane element capable of reducing the above.

[0002]

2. Description of the Related Art Some conventional reverse osmosis (hereinafter, also referred to as "RO") membranes have excellent desalination performance, water permeation performance and ionic substance separation performance. However, the conventional reverse osmosis membranes have insufficient blocking rates for non-electrolyte organic substances such as isopropyl alcohol (IPA) and substances that do not dissociate in the neutral region (for example, boron).

Further, conventionally, due to changes in natural performance of the reverse osmosis membrane over time and swelling of the reverse osmosis membrane due to chemical cleaning,
As a method for temporarily recovering the performance of the reverse osmosis membrane in which the desalination rate has decreased, a polymer aqueous solution such as polyvinyl methyl ether or tannic acid is brought into contact with the reverse osmosis membrane element to adsorb the polymer on the surface of the reverse osmosis membrane, Processing was performed aiming at the physical effect of clogging.

[0004]

However, in the conventional primary method for recovering the performance of a reverse osmosis membrane using an aqueous polymer solution, the polymer is simply adsorbed or clogged on the surface of the reverse osmosis membrane, so that the raw water is not passed through. When water is added, the polymer will be detached from the membrane surface over time, or will be detached from the membrane surface during chemical cleaning. Therefore, it was difficult to maintain the solute concentration reducing effect in the reverse osmosis membrane permeation water for a long time by the treatment.

[0005] For example, in the case of seawater desalination using a reverse osmosis membrane, it is considered that boron is a substance that is difficult to remove and is a problem. The operation was changed as an item, and the content of boron contained in seawater was set to 1.0 mg / L or less. In the case of the conventional reverse osmosis membrane, the numerical value of 1.0 mg / L or less could not always be cleared due to operating conditions or changes in natural performance of the reverse osmosis membrane over time.

In view of the above, the present invention provides a reverse osmosis membrane capable of maintaining a solute concentration reducing effect in permeated water of a reverse osmosis membrane for a long time, and separating non-electrolyte organic substances and boron which are not dissociated in a neutral region with a high blocking rate. And a reverse osmosis membrane module.

[0007]

According to the present invention, in a membrane separation device equipped with a reverse osmosis membrane element, an aqueous solution of free chlorine containing bromine is brought into contact with the reverse osmosis membrane element installed in the device so that the polyamide skin layer It was made based on the finding that the solute concentration in the reverse osmosis membrane permeate water obtained during operation is reduced by introducing bromine into the.

That is, in order to achieve the above-mentioned object, the present invention provides a membrane separation device equipped with a reverse osmosis membrane element having a polyamide skin layer, after filling the reverse osmosis membrane element into a pressure vessel in the membrane separation device. The present invention provides a method for treating a reverse osmosis membrane element, which comprises contacting the reverse osmosis membrane element with a free chlorine aqueous solution containing bromine.

According to the treatment method of the present invention, not only ionic substances which can be separated at a high rejection rate by conventional reverse osmosis membranes, but also low molecular weight non-electrolyte organic substances and boron, which have a low rejection rate by conventional reverse osmosis membranes, are used. It is possible to obtain a reverse osmosis membrane capable of separating solutes such as the above with a high rejection rate. Further, it is also possible to recover the performance of the reverse osmosis membrane in which the desalination rate is lowered due to the natural performance change of the reverse osmosis membrane over time and the swelling of the reverse osmosis membrane due to chemical cleaning. Therefore, even in the case of an existing membrane separation device using a conventional reverse osmosis membrane element, it is possible to improve the boron rejection rate of the reverse osmosis membrane by performing the reverse osmosis membrane element treatment of the present invention. It is possible to reduce the boron concentration in the permeated water to 1.0 mg or less. In addition, since the chemical treatment is performed with the free chlorine aqueous solution, the reverse osmosis membrane performance is less deteriorated due to the desorption of the treatment agent, as compared with the conventional adsorption treatment and the filling treatment of the polymer aqueous solution. Further, according to the treatment method of the present invention, the performance of the reverse osmosis membrane after treatment can prevent salt solution containing 35,000 ppm of sodium chloride by 99.7%, and thus has the same high salt rejection as the conventional reverse osmosis membrane. While having a boron concentration of 1.0
It is possible to reduce it to mg or less.

In the method for treating a reverse osmosis membrane element of the present invention, the free chlorine concentration of the free chlorine aqueous solution is 1 to 1
A range of 00 mg / L is preferred. If it is 1 mg / L or more, the rejection rate of the non-electrolyte organic substance (for example, IPA) and a substance that does not dissociate in the neutral region (for example, boron) is further improved, and if it is 100 mg / L or less, the permeation flux is lowered. It can be prevented. The free chlorine concentration is 5 to 50 mg /
The range of L is more preferable.

The bromine concentration in the free chlorine aqueous solution is 0.
The range of 5-100 mg / L is preferable. Bromine concentration is 0.
When it is 5 mg / L or more, the rejection rate of the non-electrolyte organic substance and substances that are not dissociated in the neutral region is further improved, and when the bromine concentration is 100 mg / L or less, the reduction of the permeation flow rate is prevented. The bromine concentration is more preferably in the range of 1 to 50 mg / L.

The pH of the free chlorine aqueous solution is preferably in the range of 4-11. When the pH of the free chlorine aqueous solution is 4 or more, it is possible to prevent the free chlorine from becoming chlorine gas. When the pH is 11 or less, bromine can be added to the polyamide skin layer more effectively. The pH is
The range of 4 to 6.8 is more preferable, and the range of 5 to 6.5 is particularly preferable.

The free chlorine aqueous solution is preferably demineralized water by a reverse osmosis membrane element. By using reverse osmosis membrane element demineralized water as the free chlorine aqueous solution,
It is possible to easily recover the performance of the reverse osmosis membrane mounted on the existing device and having a reduced desalination rate.

The method for treating a reverse osmosis membrane element of the present invention is preferably carried out under pressure. From the viewpoint of treatment efficiency, the pressure is preferably in the range of 0.1 to 20 MPa, more preferably 0.2 to 10 MPa, and particularly preferably 0.5 to 6 MPa.

In the method for treating a reverse osmosis membrane element of the present invention, the polyamide skin layer is a polyfunctional compound having an aromatic compound having two or more reactive amino groups and two or more reactive acid halide groups. It is preferably a polyamide skin layer formed by reacting with an acid halide compound. The reverse osmosis membrane having such a structure is excellent in desalination performance, water permeability and separation performance of ionic substances, and
Non-electrolyte organic substances such as PA and solutes such as boron that do not dissociate in the neutral region can also be separated with a high blocking rate.

Next, the present invention provides a reverse osmosis membrane module incorporating a reverse osmosis membrane element treated by the above treatment method. The reverse osmosis membrane module having such a configuration,
The conventional reverse osmosis membrane can separate ionic substances which can be separated with a high rejection rate at a higher rejection rate, and the conventional reverse osmosis membrane has a low rejection rate in the non-electrolyte organic matter (eg IPA) and neutral region. A substance that does not dissociate (for example, boron) can also be separated with a high rejection rate.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The method for treating a reverse osmosis membrane element according to the present invention is a membrane separation device equipped with a reverse osmosis membrane element having a polyamide skin layer, and the reverse osmosis membrane element is filled in a pressure vessel in the membrane separation device. After that, the reverse osmosis membrane element is contacted with a free chlorine aqueous solution containing bromine. That is, in the treatment method of the present invention, the reverse osmosis membrane element having the polyamide skin layer is brought into contact with a free chlorine aqueous solution containing bromine.

The treatment method of the present invention can be applied without particular limitation as long as it is a reverse osmosis membrane element having a polyamide skin layer. Therefore, in a new membrane separation device equipped with a reverse osmosis membrane element, after loading the reverse osmosis membrane element into the pressure vessel inside the membrane separation device, adjust the free chlorine aqueous solution containing bromine to bring it into contact with the reverse osmosis membrane element. Good. Further, also in the existing membrane separation device already equipped with the reverse osmosis membrane element, the free chlorine aqueous solution containing bromine may similarly be brought into contact with the reverse osmosis membrane element. In the treatment method of the present invention, the treatment can be performed in a state in which one or more reverse osmosis membrane elements are loaded in the pressure vessel of the membrane separation device. Therefore, the larger the size of the membrane separation device, the larger the reverse osmosis membrane. The processing time required for each element can be shortened, so that the manufacturing efficiency can be improved.

The reverse osmosis membrane element subjected to the treatment of the present invention includes, in addition to ionic substances which can obtain a high blocking rate by the conventional reverse osmosis membrane, IPA, boron and the like which have a low blocking rate by the conventional reverse osmosis membrane. Even solutes can be blocked more than before. Therefore, the treatment method of the present invention can be used for the purpose of improving performance in a membrane separation device equipped with a new or existing reverse osmosis membrane element. In this case, as for the performance of the reverse osmosis membrane mounted on the apparatus, the rejection rate of ionic substances is not reduced and the rejection rate of solutes such as IPA and boron is improved as compared with that before treatment.

Further, in a membrane separation device equipped with an existing reverse osmosis membrane element, the desalination rate is lowered due to a change in natural performance of the reverse osmosis membrane over time, and the reverse osmosis membrane is swollen and desalted by chemical washing. When the rate decreases, the solute concentration in the permeate of the reverse osmosis membrane can be reduced by performing the reverse osmosis membrane treatment of the present invention. Therefore, the treatment method of the present invention can also be used for the purpose of recovering the performance of the reverse osmosis membrane. In this case, the rejection rate of ionic substances in the reverse osmosis membrane mounted on the existing device is improved as compared with that before the treatment. Therefore, the treatment method of the present invention can also be used for the purpose of improving the blocking performance of ionic substances, which was the target of blocking in the conventional reverse osmosis membrane.

The free chlorine aqueous solution containing bromine used in the above treatment can be prepared, for example, by dissolving a bromine compound and free chlorine in water. The bromine compound is not particularly limited as long as it can be dissolved in water. For example, sodium bromide, potassium bromide, calcium bromide, magnesium bromide, ammonium bromide, lithium bromide, cadmium bromide, germanium bromide, cobalt bromide, strontium bromide, cesium bromide, tungsten bromide, Iron bromide,
Brominated compounds such as tellurium bromide, copper bromide, barium bromide, manganese bromide, hydrogen bromide and the like can be mentioned. Of these, alkali metal bromine compounds and alkaline earth metal bromine compounds are preferable, and alkali metal bromine compounds are more preferable.

Such a free chlorine aqueous solution containing bromine is added with free chlorine to water originally containing bromine or desalted water of a reverse osmosis membrane element, such as seawater and groundwater, and the pH is adjusted as necessary. It can be adjusted within the predetermined range. Above all, by using demineralized water of the reverse osmosis membrane element, the performance of the reverse osmosis membrane installed in the existing device is improved,
Performance recovery can be performed easily.

In the method for treating a reverse osmosis membrane element of the present invention, the concentration of free chlorine in the free chlorine aqueous solution is 1 to 1
The range of 00 mg / L is preferable, and the range of 5 to 50 mg / L is more preferable. If it is 1 mg / L or more, the rejection rate of the non-electrolyte organic substance (for example, IPA) and the substance that does not dissociate in the neutral region (for example, boron) is further improved, and 1
When the amount is 00 mg / L or less, the permeation flux can be prevented from decreasing.

The bromine concentration in the free chlorine aqueous solution is 0.
The range of 5 to 100 mg / L is preferable, and 1 to 50 mg / L
The range of L is more preferable. When the bromine concentration is 0.5 mg / L or more, the rejection rate of non-electrolyte organic substances and substances that do not dissociate in the neutral region is further improved, and the bromine concentration is 100 m.
When it is not more than g / L, the permeation flow rate is prevented from decreasing.

With respect to the bromine concentration, the pH of the free chlorine aqueous solution is preferably in the range of 4 to 11, more preferably 4
The range is from 6.8 to 6.8, and the range from 5 to 6.5 is particularly preferable. When the pH of the free chlorine aqueous solution is 4 or more, it is possible to prevent the free chlorine from becoming chlorine gas. When the pH is 11 or less, bromine can be added to the polyamide skin layer more effectively.

The reverse osmosis membrane having a polyamide skin layer in which the treatment method of the present invention is used is not particularly limited. Excellent in desalination performance, water permeability and separation performance of ionic substances,
From the viewpoint that non-electrolyte organic substances such as IPA and solutes such as boron that do not dissociate in the neutral region can be separated with a high rejection rate,
An aromatic compound having two or more reactive amino groups, and 2
A reverse osmosis membrane having a polyamide skin layer formed by reacting a polyfunctional acid halide compound having one or more reactive acid halide groups is preferable.

As the reverse osmosis membrane having the polyamide skin layer, for example, an aromatic compound having two or more reactive amino groups and two or more reactive acid halide groups are provided on a porous support. The thing which formed the polyamide skin layer by making it react with the polyfunctional acid halide compound which it has, etc. can be mentioned.

The aromatic compound having two or more reactive amino groups (hereinafter also referred to as "polyfunctional amine") is not particularly limited, and examples thereof include m-phenylenediamine, p-phenylenediamine, 1,3,5. -Triaminobenzene, 1,
2,4-triaminobenzene, 8,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,4-diaminoanisole, amidole, xylylenediamine and the like can be mentioned. Preferred are m-phenylenediamine, p-phenylenediamine and triaminobenzene. Of these, m-phenylenediamine and triaminobenzene are preferable.

In addition to these aromatic polyfunctional amines, aliphatic or alicyclic polyfunctional amines may be mixed and used. As such an aliphatic polyfunctional amine, for example,
Ethylenediamine, propylenediamine, tris (2-
Aminoethyl) amine and the like. Further, examples of the alicyclic polyfunctional amine include 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexanepiperazine, 2,5-dimethylpiperazine, 4-aminomethylpiperazine and the like. To be

The polyfunctional acid halide (hereinafter also referred to as "acid halide") is not particularly limited, and examples thereof include aromatic, aliphatic, alicyclic and other polyfunctional acid halides, and preferred. Is an aromatic polyfunctional acid halide.

Examples of the aromatic polyfunctional acid halides include trimesic acid chloride, terephthalic acid chloride, isophthalic acid chloride, biphenyldicarboxylic acid chloride, naphthalenedicarboxylic acid dichloride, benzenetrisulfonic acid chloride, benzenedisulfonic acid chloride, Chlorosulfonylbenzene dicarboxylic acid chloride and the like can be mentioned. Of these, monocyclic aromatic compounds are preferred.

Examples of the aliphatic polyfunctional acid halides include propane tricarboxylic acid chloride, butane tricarboxylic acid chloride, pentane tricarboxylic acid chloride, glutaryl halide, adipoyl halide and the like.

Examples of the alicyclic polyfunctional acid halides include cyclopropane tricarboxylic acid chloride, cyclobutane tetracarboxylic acid chloride, cyclopentane tricarboxylic acid chloride, cyclopentane tetracarboxylic acid chloride, cyclohexane tricarboxylic acid chloride and tetrahydro. Furan tetracarboxylic acid chloride, cyclopentane dicarboxylic acid chloride, cyclobutane dicarboxylic acid chloride, cyclohexane dicarboxylic acid chloride, tetrahydrofurandicarboxylic acid chloride and the like can be mentioned.

The porous support is not particularly limited as long as it can support the polyamide skin layer, and various materials such as polysulfone, polyarylethersulfone such as polyethersulfone, polyimide, polyvinylidene fluoride and the like can be used. In particular, polysulfone, because of its chemical, mechanical and thermal stability,
A porous support membrane made of polyarylethersulfone is preferably used. Such a porous support usually has a thickness of about 25 to 125 μm, preferably about 40 to 75 μm, but is not necessarily limited thereto.

Next, the polyfunctional amine component and the acid halide component are interfacially polymerized to form a polyamide skin layer containing a crosslinked polyamide as a main component on the porous support. For example, a first layer made of a solution containing the polyfunctional amine component is formed on a porous support by coating or the like, and then a layer made of a solution containing the acid halide component is formed by coating or the like. Is formed on the above porous support and subjected to interfacial polycondensation to form a thin film (polyamide skin layer) made of crosslinked polyamide on the porous support.

The solution containing a polyfunctional amine is used for facilitating the film formation or improving the performance of the obtained reverse osmosis membrane. Further, for example, a polymer such as polyvinyl alcohol, polyvinylpyrrolidone or polyacrylic acid, A small amount of polyhydric alcohol such as sorbitol, sorbitol, glycerin, etc. may be contained.

In order to increase the permeation flux, a polyfunctional amine is used.
Or a solution containing an acid halide component
Solubility parameters (specific
Kaihei 8-224452) is 8-14 (cal /
cm³)^1/2Compounds of can be added. The dissolution
The degree parameter is the heat of vaporization of the liquid by ΔHcal / m
ol, molar volume is Vcm³/ Mol, (△ H
/ V)^1/2(Cal / cm ³)^1/2The amount defined by
U As a substance with such solubility parameters
Is, for example, alcohols, ethers, ketones,
Steals, halogenated hydrocarbons, sulfur-containing compounds, etc.
Specifically, it is specifically described in JP-A-8-224452.
The substance is.

The amine salts described in JP-A-2-187135, such as salts of tetraalkylammonium halides and trialkylamines with organic acids, also absorb the amine solution onto the support to facilitate film formation. To improve
From the viewpoint of accelerating the condensation reaction, it is preferably used in a solution containing a polyfunctional amine, a solution containing an acid halide component, or both of the above solutions.

Sodium dodecylbenzene sulfonate,
A surfactant such as sodium dodecyl sulfate or sodium lauryl sulfate may be contained in the solution containing the polyfunctional amine or the solution containing the acid halide component, or both of the solutions. These surfactants are effective in improving the wettability of the solution containing the polyfunctional amine to the porous support.

In order to accelerate the polycondensation reaction at the interface, hydrogen halide formed in the interface reaction is added to a solution containing a polyfunctional amine or a solution containing an acid halide component, or both of the solutions. It is also advantageous to use sodium hydroxide or trisodium phosphate capable of removing cis, or to use an acylation catalyst or the like as a catalyst.

In the solution containing the acid halide and the solution containing the polyfunctional amine, the concentrations of the acid halide and the polyfunctional amine are not particularly limited, but the acid halide is usually 0.01 to 5 mass. %, Preferably 0.0
5 to 1% by mass, and the polyfunctional amine is usually 0.1 to 1
It is 0% by mass, preferably 0.5 to 5% by mass.

In this way, after coating the porous support with the solution containing the polyfunctional amine, and then coating the solution containing the polyfunctional acid halide compound thereon, the excess solution is removed. , Then usually about 20-150
C., preferably about 70-130.degree. C. for about 1-10 minutes,
It is preferably dried by heating for about 2 to 8 minutes to form a water-permeable thin film made of crosslinked polyamide. The thickness of this thin film is usually about 0.05 to 2 μm, preferably about 0.
It is in the range of 10 to 1 μm.

In the treatment method of the present invention, one or a plurality of reverse osmosis membrane elements having a polyamide skin layer are loaded in a pressure vessel of a membrane separator, and the reverse osmosis membrane element is contacted with a free chlorine aqueous solution containing bromine. Let As mentioned above, this contact is preferably performed under pressure. From the viewpoint of processing efficiency, this pressure is, for example, 0.1 to 20M.
It is in the range of Pa, preferably in the range of 0.2 to 10 MPa, and more preferably in the range of 0.5 to 6 MPa.

When the reverse osmosis membrane element is contacted with a free chlorine aqueous solution containing bromine, the bromine-containing free chlorine aqueous solution is applied to the reverse osmosis membrane element, for example, 5 to 120.
It is advisable to pass water for 15 minutes, preferably for 15 to 60 minutes. If the water passage time is 5 minutes or more, the rejection rate of non-electrolytic organic substances and substances that do not dissociate in the neutral range such as boron is further improved, and if the water passage time is 120 minutes or less, the permeation flux is lowered. It can be prevented.

Bromine atoms are added to the polyamide skin layer in the reverse osmosis membrane treated by the treatment method of the present invention. It should be noted that chlorine atoms may or may not be added to the polyamide skin layer. The fact that the polyamide skin layer has bromine can be confirmed by, for example, electron spectroscopy (ESCA).

Bromine contained in the polyamide skin layer is
It may be atomic or ionic. A substance other than bromine may be added to the polyamide skin layer as long as the effect of the present invention is not impaired. Further, bromine is preferably added to the aromatic compound portion of the polyamide skin layer.

The polyamide skin layer of the reverse osmosis membrane treated by the treatment method of the present invention varies depending on the reaction conditions at the time of forming the polyamide skin layer, but it depends on the nitrogen atom (N) constituting the bromine atom (Br) and the amino group. ) And the ratio (Br / N)
Is preferably 0.1 or more and 1.0 or less.
When this ratio is 0.1 or more, the non-electrolyte organic substance and the substance that does not dissociate in the neutral region can be separated with a higher blocking rate. Further, when the ratio is 1.0 or less, the non-electrolyte organic substance and the substance that does not dissociate in the neutral region can be separated with a higher blocking rate, and the permeation flux is prevented from becoming too low, and the operating pressure is high. It can be prevented from becoming too much, which is economically advantageous. The more preferable range of the ratio is 0.15 or more and 0.7 or less, and the optimum range is 0.2 or more and 0.5 or less.

As described above, the reverse osmosis membrane module incorporating the reverse osmosis membrane element treated by the treatment method of the present invention is suitable for desalination by desalting brackish water, seawater or the like, or for producing ultrapure water. It can be preferably used. It can also be used for removing and collecting a pollution source or an effective substance contained in industrial wastewater, which is a cause of pollution such as dyeing wastewater and electrodeposition paint wastewater, and can contribute to closing the wastewater.
In addition to this, it can be used for water treatment such as concentration of active ingredients and removal of harmful components such as tap water and sewage in fields such as food industry.

[0049]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Production Example 1) m-phenylenediamine (3
%), Sodium lauryl sulfate (0.25% by weight), triethylamine (2% by weight) and camphorsulfonic acid (4% by weight) were applied to the porous support (polysulfone ultrafiltration membrane). After that, the excess aqueous solution was removed to form a layer of the aqueous solution on the support. Furthermore, on this layer, chlorite trimesic acid (0.1% by weight) and chlorite isophthalate (0.
15% by weight) in an isooctane solution was applied and then kept in a dryer at 120 ° C. for 3 minutes to form a polymer thin film (polyamide skin layer) on the porous support to obtain a reverse osmosis membrane. In this reverse osmosis membrane, the average thickness of the porous support was 50 μm, and the average thickness of the polyamide skin layer was 0.2 μm.

Example 1 pH 6.5, 3.5 at 25 ° C.
Using a mass% NaCl aqueous solution as raw water, 5.49MP
a RO membrane element (diameter 201 mm, length 201 mm) having a rejection rate of salt of 99.7% and a permeated water amount of 15 m ³ / day when evaluated under conditions of pressurization and concentrated water flow rate of 90 L / min 1016 mm) were loaded in series in a pressure vessel of a seawater desalination membrane separator. Then, the total evaporation residue (hereinafter referred to as "TDS") concentration in seawater desalinated by the RO membrane element was 150 m.
g / L of water was prepared so that the content of free chlorine was 20 mg / L, sodium bromide was 20 mg / L, and the pH was 6.0, and this solution was passed under an operating pressure of 1.5 MPa for 30 minutes to obtain the RO of the present invention. A membrane treatment was performed.

When the constituent elements of this treated RO membrane element were examined by ESCA, the ratio of the bromine atom (Br) to the nitrogen atom (N) of the amino group (B
The r / N) was 0.27.

Seawater (TDS concentration 3.5% by mass, boron 4.7%) was supplied to the treated RO membrane element as a supply liquid.
(mg / L, pH 6.8, temperature 26 ° C.), water was passed through, and operation was performed under the conditions of a permeated water amount of 90 m ³ / day and a recovery rate (ratio of the permeated water amount to the supplied water amount) of 40%. As a result, the quality of the permeated water obtained was 100 mg / L of TDS,
The boron concentration was 0.4 mg / L.

Comparative Example 1 pH 6.5, 3.5 at 25 ° C.
When the mass% NaCl aqueous solution is used as raw water, the salt rejection rate is 9 under the conditions of 5.49 MPa pressurization and concentrated water flow rate of 90 L / min.
Six RO membrane elements (diameter 201 mm, length 1016 mm) having a polyamide skin layer having a performance of 9.7% and a permeated water amount of 15 m ³ / day were loaded in series in a pressure vessel of a seawater desalination membrane separation device. .

Thereafter, seawater (TDS concentration 3.5% by mass, boron 4.7 mg / L, pH 6.8, temperature 26 ° C.) was passed as a feed liquid without performing the RO membrane treatment of Example 1. The operation was performed under the conditions of a permeated water amount of 90 m ³ / day and a recovery rate (ratio of the permeated water amount obtained to the supplied water amount) of 40%. As a result, the quality of the permeate obtained was TDS150.
The mg / L and boron concentration were 0.7 mg / L.

Example 2 Seawater (TDS concentration 3.5% by mass, boron 4.7 mg / L, pH 6.8, temperature 26 ° C.)
Membrane separation device that passes water and is operating for the purpose of desalination (permeate volume 70 m ³ / day, recovery rate 40%, RO element 5
In this series loading), in the RO membrane element in which the natural performance change of the RO membrane with time and the decrease in desalination rate due to the swelling of the RO membrane due to chemical cleaning occurred, the TDS concentration of 300 mg desalinated by the RO membrane element / L water, free chlorine 20 mg / L, sodium bromide 20 mg /
L, pH 6.0, operating pressure 1.5M
The RO membrane treatment of the present invention was performed by passing water at Pa for 30 minutes.

When the constituent elements of this treated RO membrane element were examined by ESCA, the ratio of the bromine atom (Br) to the nitrogen atom (N) of the amino group (B
The r / N) was 0.15.

After the treatment, the seawater desalination was restarted under the original operating conditions, and the obtained permeate was analyzed.
The concentration was 0 mg / L and the boron concentration was 0.9 mg / L. The water quality of the permeate before treatment was TDS 300 mg / L and the boron concentration was 1.3 mg / L.
It was confirmed that the membrane treatment improved the water quality of the RO permeate.

From the above results, the reverse osmosis membrane element subjected to the treatment of the present invention has an extremely high rejection rate not only for ionic substances such as salt but also for boron and the like which are not dissociated in the neutral region. Recognize.

[0060]

As described above, the method for treating a reverse osmosis membrane element of the present invention can shorten the treatment time required for each reverse osmosis membrane element, and since the chemical treatment is carried out by the free chlorine aqueous solution, Compared to adsorption treatment and clogging treatment of polymer aqueous solution, the deterioration of reverse osmosis membrane performance due to desorption of the treatment agent is less. Therefore, it can be used not only as a performance improving means for the reverse osmosis membrane element in the membrane separation device but also as a performance recovery means in the membrane separation device after operation.

The treated reverse osmosis membrane element is excellent in desalination performance, water permeability and separation performance of ionic substances, and also has a high rejection rate of non-electrolyte organic substances and non-dissociated substances in the neutral region. Can be separated by. In particular, in desalination of seawater, not only the total evaporation residue (TDS) in seawater can be removed, but also boron, which is difficult to remove because it is not dissociated in the neutral region, can be removed with a high rejection rate.

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 500277526             Hydronautics             HYDRANAUTICS             United States California             92054 Oceanside, Jones             Road 401             401 Jones Road Ocean             side, California 92054               The United States             of America (72) Inventor Masaaki Ando             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Terutaka Watanabe             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Masahiko Hirose             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Hisao Hachisuka             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Mark Wilf             United States California 92054             -Shanside, Jones Road 401             Within Hydronautics (72) Inventor Craig Bartels             United States California 92054             -Shanside, Jones Road 401             Within Hydronautics (72) Inventor Keith Andes             United States California 92054             -Shanside, Jones Road 401             Within Hydronautics F-term (reference) 4D006 GA03 MB06 MC54X MC71X                       NA54 NA64 PB03 PB08 PC02                       PC21

Claims (9)

[Claims] 1. A membrane separator equipped with a reverse osmosis membrane element having a polyamide skin layer, wherein the reverse osmosis membrane element is filled in a pressure vessel inside the membrane separator, and then the reverse osmosis membrane element contains free chlorine containing bromine. A method for treating a reverse osmosis membrane element, which comprises contacting an aqueous solution. 2. The free chlorine concentration of the free chlorine aqueous solution is
The method for treating a reverse osmosis membrane element according to claim 1, wherein the treatment amount is 1 to 100 mg / liter (L). 3. The bromine concentration in the free chlorine aqueous solution is
The method for treating a reverse osmosis membrane element according to claim 1 or 2, wherein the treatment amount is 0.5 to 100 mg / L. 4. The pH of the free chlorine aqueous solution is 4-11.
The method for treating a reverse osmosis membrane element according to claim 1, wherein the reverse osmosis membrane element is in the range. 5. The method for treating a reverse osmosis membrane element according to claim 1, wherein the free chlorine aqueous solution is demineralized water by a reverse osmosis membrane element. 6. The method of claim 1, wherein the contacting is under pressure.
6. The method for treating a reverse osmosis membrane element according to any one of items 1 to 5. 7. The method for treating a reverse osmosis membrane element according to claim 6, wherein the pressure is in the range of 0.1 to 20 MPa. 8. The polyamide skin layer is formed by reacting an aromatic compound having two or more reactive amino groups with a polyfunctional acid halide compound having two or more reactive acid halide groups. The method for treating a reverse osmosis membrane element according to any one of claims 1 to 7, which is a polyamide skin layer. 9. A reverse osmosis membrane module comprising a reverse osmosis membrane element treated by the treatment method according to any one of claims 1 to 8.